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Biomedical subjects

G Nilsen

Publications and source records attributed to G Nilsen.

At least 19 recordsLinked to original sources
PubMed2000

[Diagnosis of breast diseases with magnetic resonance tomography].

Magnetic resonance imaging (MRI) of the breast is currently used for evaluation of both parenchymal disease and silicone gel implants. MRI is widely recognised as the most accurate imaging method for evaluation of breast implant integrity. Knowledge of the MRI appearance of the different types of implants and the possible complications of their use is important for diagnosis in these patients. The use of contrast-enhanced MRI in breast cancer diagnosis has been investigated thoroughly during the last decade. It is a sensitive imaging method to detect breast pathology, and may have an important diagnostic impact in carefully selected patient groups. The development of new MR techniques may improve the utility of MR in breast cancer diagnosis, treatment and research.

Biopsy↗
PubMed1999

[Medullary compression in metastatic cancer].

Cancer patients with spinal cord compression may develop irreversible neurological deficit. The clinical picture implies back pain and subsequent neurological deficit. There is always a danger of rapid deterioration of the patient's condition. If spinal cord compression is suspected, the case is an emergency. MRI should be preferred in the diagnostic work-up, and corticosteroids be administered promptly. Radiation therapy or surgical treatment should be started as soon as possible. Patient outcome is related to the degree of neurological deficit at the start of treatment.

Combined Modality Therapy↗
PubMed1998

Cerebral MRI of very low birth weight children at 6 years of age compared with the findings at 1 year.

BACKGROUND: We have previously reported the results of cerebral MRI examinations in an unselected year cohort of very low birth weight (VLBW) infants at one year of corrected age. Twenty-one (78 %) of 27 infants had abnormal myelination, mainly in the central occipital white matter (COWM) and in the centrum semiovale (CS), seen on T2-weighted images. Twelve infants had irregular and dilated lateral ventricles. We speculated whether these findings indicated perinatal periventricular leukomalacia (PVL). Only two infants had completely normal MRI at age 1 year. OBJECTIVE: To determine whether the abnormal myelination seen at 1 year of age, was still present, either as delayed myelination or as gliosis caused by perinatal PVL. MATERIALS AND METHODS: In the present study, we report the results of follow-up cerebral MRI in 20 of these infants at 6 years of age. RESULTS: Most of the children with MRI deviations at 1 year still had abnormalities at 6 years. Abnormal myelination in the central occipital white matter combined with abnormalities in the CS or with ventricular dilatation at age 1 year, presented as gliosis in 12 of 13 children at 6 years of age. Abnormalities solely in the COWM at age 1 year had normalised in two of five children and persisted as delayed myelination in three at age 6 years. Gliotic changes in periventricular white matter were found in 12 of 20 children (60 %). Areas most affected were the CS (11 children) and the COWM (9 children). Delayed myelination in COWM was found in six children (30 %), combined with gliosis in CS in three children. Twelve infants had ventricular dilatation both at 1 and 6 years of age. CONCLUSIONS: The MRI correlates of PVL, i. e. gliosis and ventricular dilatation, are common findings on cerebral MRI at 6 years of age in VLBW infants.

Brain↗
PubMed1998

Can cerebral MRI at age 1 year predict motor and intellectual outcomes in very-low-birthweight children?

This follow-up study reports on cerebral MRI findings in 20 very-low-birthweight (VLBW) infants without disabilities at age 1 year in relation to motor, intellectual, and perceptual function at age 6 years. MRI findings, anthropometrics, and Bayley Scales of Infant Development scores at age 1 year as predictors of psychomotor status at age 6 years are also evaluated and compared. Outcome parameters were the Peabody Developmental Motor Scales and the Wechsler Preschool and Primary Scale of Intelligence. The results show that infants with myelin hyperintensities including the centrum semiovale or with occipital hyperintensities with associated ventricular dilatation at age 1 scored lower on the Peabody Gross Motor Locomotion Scale at age 6 than infants with normal myelination or with isolated occipital hyperintensities. This may indicate damage to motor fibers caused by perinatal periventricular leukomalacia. No relation was found between abnormal MRI findings at age 1 and later fine motor, intellectual, and perceptual function. Comparing different age 1-year predictors, an abnormality score defined by MRI was used as an independent predictor of gross motor locomotion function at age 6 years. However, the Bayley Mental Development Index scores and weight at age 1 were more important predictors of later motor and intellectual outcome, respectively, than MRI findings. It is recommended that cerebral MRI should not be used routinely to examine VLBW infants without disabilities at 1 year of age.

Age Factors↗
PubMed1997

Cerebral magnetic resonance imaging and mental and motor function of very low birth weight children at six years of age.

In this follow-up study, 20 of a geographically based year cohort of 31 surviving non-disabled VLBW (birthweight < 1500 g) children were examined at six years of age. The aim of the study was to relate cerebral MRI findings to neuro-development in these non-disabled children at six years of age. All MRI scans were evaluated for myelination pattern, periventricular gliosis, ventricular dilation and cortical atrophy. The Peabody motor test and the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) were used in the evaluation of motor, mental and perceptual function. A diagnosis of attention deficit disorder with hyperactivity was made based on the examiner's impression of the child during the examination and based on the parent's history. We found that ten (50%) of the children had periventricular gliosis, mainly in centrum semiovale (CS) (nine children) and in central occipital white matter (COW) (six children). Gliosis in CS was related to lower scores on the Peabody gross motor test for locomotion, indicating involvement of corticospinal tracts. Additional gliosis in COW was related to both fine motor and gross motor impairments. We speculate that this indicates damage to both motor and visual pathways, affecting eye-hand coordination and balance function. No relationship between MRI deviations at six years and mental function based on performance, verbal and total IQ scores was found. However, there was a significant relationship between periventricular gliosis in COW and C5 and low scores on the WPPSI performance subtests: Picture completion test and Block design test. This may indicate visual and spatial perception problems, caused by damage to posterior visual pathways and occipito-thalamic tracts dealing with visuo-motor integration.

Analysis of Variance↗
PubMed1997

MnDPDP for MR imaging of the liver. Results of an independent image evaluation of the European phase III studies.

PURPOSE: To evaluate the diagnostic efficacy of mangafodipir trisodium (MnDPDP, Teslascan) as a new contrast agent for MR imaging of the liver based on an independent evaluation of the MR images from the European phase III studies. MATERIAL AND METHODS: MR imaging of the liver was done at 0.5-2.0 T in 17 European centres and included T1-weighted spin-echo and gradient-echo sequences before and after administration of MnDPDP to patients at a dose of 5 mumol/kg b.w. T2-weighted images were also obtained in all cases before the i.v. injection of the agent. Images of a total of 592 patients were evaluated by 4 independent experienced radiologists who were not involved in the on-site clinical trials. RESULTS: Statistically significantly more lesions were detected (p = 0.0014) in MnDPDP-enhanced T1-weighted MR images than in unenhanced images. T1-weighted gradient-echo sequences were found to be superior to T1-weighted spin-echo sequences after injection of MnDPDP. The post-contrast images were found to be statistically significantly superior to the pre-contrast images in confidence in the presence of a lesion (p < or = 0.0001), quality of lesion delineation (p < or = 0.0001), lesion conspicuity (p < or = 0.0001) and in the confidence in the diagnosis of a lesion (p = 0.001). CONCLUSION: This independent evaluation of the European phase III trials confirmed the superiority of MnDPDP-enhanced MR images over unenhanced images for lesion detection and characterization.

Adult↗
PubMed1997

Nod factor-induced expression of leghemoglobin to study the mechanism of NH4NO3 inhibition on root hair deformation.

Nod factors secreted by Rhizobium leguminosarum by, viciae induce root hair deformation, the formation of nodule primordia, and the expression of early nodulin genes in Vicia sativa (vetch). Root hair deformation is induced within 3 h in a small, susceptible zone (+/-2 mm) of the root. NH4NO3, known to be a potent blocker of nodule formation, inhibits root hair deformation, initial cortical cell divisions, and infection thread formation. To test whether NH4NO3 affects the formation of a component of the Nod factor perception-transduction system, we studied Nod factor-induced gene expression. The differential display technique was used to search for marker genes, which are induced within 1 to 3 h after Nod factor application. Surprisingly, one of the isolated cDNA clones was identified as a leghemoglobin gene (VsLb1), which is induced in vetch roots within 1 h after Nod factor application. By using the drug brefeldin A, it was then shown that VsLb1 activation does not require root hair deformation. The pVsLb1 clone was used as a marker to show that in vetch plants grown in the presence of NH4NO3, Nod factor perception and transduction leading to gene expression are unaffected.

Base Sequence↗
PubMed1997

Pulmonary embolism: detection with MR perfusion imaging of lung--a feasibility study.

PURPOSE: To evaluate the feasibility of magnetic resonance (MR) perfusion imaging in the human lung to help detect perfusion defects distal to suspected pulmonary embolism. MATERIALS AND METHODS: Seven patients suspected of having pulmonary embolism first underwent ventilation-perfusion lung scintigraphy followed by MR perfusion imaging with rapid acquisition of two sets of dynamic images in the coronal and transaxial planes. A bolus of 0.05 mmol per kilogram of body weight gadopentetate dimeglumine or gadodiamide was administered. Single images obtained in each section that showed peak signal intensity from the first passage of contrast material were evaluated visually. An analysis of change in signal intensity over time was performed both on a pixel-by-pixel basis and in selected regions of interest. RESULTS: In the seven patients, a total of 18 regions of lung tissue with perfusion defects were shown on the ventilation-perfusion scans. In 16 of these regions, MR perfusion images showed a reduced peak signal intensity during first passage of the contrast agent. Perfusion defects could be detected in both the coronal and the transaxial planes on MR perfusion images. CONCLUSION: MR perfusion imaging was feasible for detection of perfusion defects distal to a pulmonary embolism.

Adult↗
PubMed1995

[Magnetic tomography in the examination of edema and pain in the leg].

Magnetic resonance imaging (MRI) was used to investigate 38 patients suffering from leg oedema or pain of various etiology. Spin echo series with 10 mm transverse slices of both legs were obtained. Soft tissue changes were visualized best by T2-weighted sequences. Characteristic changes could be observed by MR images of patients with closed compartment syndrome (n = 2), chronic lymph oedema (n = 10) and post-reconstructive leg oedema following vascular surgery (n = 14). MRI can also show typical soft tissue changes in patients with deep vein thrombosis (n = 5) or post-thrombotic syndrome (n = 3). For most of these conditions, the diagnosis can usually be established using simpler methods. However, MRI is an excellent supplementary method for showing soft tissue changes, and is a promising way of investigating conditions that may give rise to leg oedema and pain.

Adult↗
PubMed1995

Alterations in intracranial volume following cross-clamping of the descending thoracic aorta in pigs--an experimental study using MRI.

OBJECTIVES: To determine whether alterations in intracranial volume occurred following cross-clamping of the descending thoracic aorta in pigs. DESIGN AND SETTING: Laboratory animal study. MATERIALS: Eight pigs undergoing cross-clamping of the descending thoracic aorta for 30 min. CHIEF OUTCOME MEASURES: A Philips Gyroscan T5-II Release 3 (0.5 T) was used to obtain intracranial images before cross-clamping, during cross-clamping and after declamping. The ventricular volume was measured on Spin Echo T1-weighted images. The signal intensity of the cerebral tissue was measured on Spin Echo T2-weighted images. Increased signal intensity of the cerebral tissue relative to an external reference was used as an indicator of cerebral oedema. MAIN RESULTS: The ventricular volume decreased to 89% (p < 0.01) of the baseline value after 5 min of cross-clamping. At 5 min after declamping the ventricular volume decreased further to 71% (p < 0.01). At 25 min after declamping the ventricular volume had returned to the baseline value. The signal intensity of the cerebral tissue did not differ from baseline values following aortic cross-clamping. CONCLUSIONS: In this study, ventricular volume decreased following cross-clamping of the descending thoracic aorta. Since no cerebral oedema was observed, the decrease of ventricular volume was most likely due to increased intracranial blood volume.

Animals↗
PubMed1994

Perianal fistulas: use of MR imaging for diagnosis.

PURPOSE: To evaluate use of magnetic resonance (MR) imaging with saline solution as contrast agent in diagnosis of perianal fistulous disease. MATERIALS AND METHODS: Spin-echo intermediate-, T2-, and T1-weighted images were obtained before and after instillation of saline solution into anal fistulas in 12 of 16 consecutive patients. In four patients without secretory fistulas, images were obtained without contrast enhancement. RESULTS: Fistulous tracts were found in 13 patients, fluid cavities in 13, secondary fibrotic tracts in two, and normal perirectal tissue in one. The extent of fistulas and fluid collections was better delineated or more conspicuous on contrast-enhanced images in eight and 10 examinations, respectively, in part due to expansion of collapsed portions of the fistulous system. T2-weighted images were sufficient for diagnosis. CONCLUSION: MR imaging with saline solution as contrast agent may improve visualization of fistulas and their relationship to normal anatomic structures in patients with complex fistulous systems with relatively sparse secretion.

Adult↗
PubMed1994

Nuclear magnetic resonance spectroscopy: biochemical evaluation of brain function in vivo and in vitro.

Nuclear magnetic resonance spectroscopy (MRS) offers a unique opportunity to monitor mmolar concentrations of high energy phosphates, glucose, lactate and amino acids. The possibility of obtaining information about chemical constituents noninvasively is of great importance. MRS and chemical shift imaging (CSI) are emerging as tools for tumor grading, monitoring of treatment, ischemia research, in pediatric research for follow-up of children with borderline mental retardation, for defining brain death and to define epileptic foci. It is important to know which cell type (neuronal or glial) shows changes as a result of external manipulations (e.g. excitotoxins) or internal changes (brain pathology). Metabolic studies have been carried out on brain cell cultures. By using 13C labeled glucose and acetate in combination with 13C MRS it was shown that astrocytes release lactate, glutamine, citrate and alanine and that cerebral cortical neurons use glutamine released from astrocytes as a precursor for GABA synthesis. An important feature in MRS is the localization of N-acetyl aspartate in neurons, since this enables monitoring of neuronal reactions, such as survival after neurotoxic insults. Recent advances have yielded high speed functional echo planar imaging (EPI) techniques that are sensitive to changes in cerebral blood volume, blood flow and blood oxygenation (Functional MRI). During cognitive task performance, local alterations in neuronal activity induce local changes in cerebral metabolism and cerebral perfusion, which can now be detected with MRI.

Animals↗
PubMed1994

The use of MRI in the diagnosis of chronic lymphedema of the lower extremity.

Magnetic resonance imaging (MRI) was used in 10 female patients with chronic lymphedema of the leg. Soft tissue changes in lymphedema is best visualized by T2-weighted sequences. Three patients had a characteristic honeycomb pattern of the subcutanous tissue, whereas the other patients had either diffuse edema or a reticular pattern. The muscular compartments were normal, while the dermis was significantly thickened in 9 out of 10 patients. In conclusion, characteristic changes were observed in MR images of patients with chronic lymphedema of the leg. Further investigations are necessary to evaluate the role of MRI as an aid in the choice of therapy.

Evaluation Studies as Topic↗
PubMed1993

Posterior cranial fossa dimensions in the Chiari I malformation: relation to pathogenesis and clinical presentation.

Skull dimensions were measured on lateral skull radiographs in 33 adult patients with MRI-verified Chiari I malformations and in 40 controls. The posterior cranial fossa was significantly smaller and shallower in patients than in controls. In the patients, there was a positive correlation between posterior fossa size and the degree of the cerebellar ectopia, which might indicate that a posterior cranial fossa which was originally too small had been expanded by the herniation of hindbrain structures at an early stage. Pyramidal signs and cerebellar symptoms and signs, which may be due to compression of neural structures, were associated with a large degree of ectopia and a relatively large posterior cranial fossa. Syringomyelia and headache, which may be due to the valve action of the herniated cerebellar tissue, were not associated with a particularly large posterior fossa or herniation. No special clinical presentation was associated with a very small posterior cranial fossa, which may indicate that a small posterior cranial fossa per se has little or no clinical significance, although it may be the primary developmental anomaly.

Adult↗
PubMed1993

Cerebral magnetic resonance imaging (MRI) and mental and motor function of very low birth weight infants at one year of corrected age.

Thirty-one (77.5%) of a year cohort of 40 surviving infants with birth weight < 1500 grams were seen on follow-up examination at one year of corrected age. At neurological evaluation 20 infants were normal (Group 1), seven infants were considered at risk (Group 2), and four infants had cerebral palsy (Group 3). Assessment on the Bayley Scales gave significantly lower mean scores in Group 3 compared with Group 1, both on the Mental Index (63 versus 102, p < 0.001) and on the Psychomotor Index (PDI) (60 versus 94, p < 0.005). Mean PDI score in Group 2 was significantly lower than in Group 1 (74 versus 94, p < 0.005). Cerebral MRI was performed in 27 infants. Of the 19 infants in Group 1 examined with MRI, 14 infants showed deviating changes in both myelin deposition and maturation (2). In all 14 infants the central occipital white matter was affected and in three infants also the centrum semiovale, both areas correspond to predilection sites for periventricular leukomalacia (PVL). Five infants had irregular shape of the occipital horns of the lateral ventricles. These findings may also represent the end stages of PVL (4). Only four out of seven infants were examined with MRI in Group 2. However, three infants had deviating myelination and three had irregular shape of the posterior horns. In Group 3 all infants were examined with MRI and all had deviating myelination and irregular and slightly dilated posterior horn. There was a significant correlation between abnormally dilated occipital horns seen with MRI, and cerebral palsy and low scores on the Denver and the Bayley tests.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrophy↗
PubMed1993

Minor structural brain changes in young drug abusers. A magnetic resonance study.

Twenty-three drug abusers and seventeen controls underwent clinical neurological examinations and magnetic resonance imaging (MRI) of the brain. The drug abuse encompassed cannabis, inhalants, opiates, psychedelics, amphetamines, and cocaine but not necessarily all drugs in all persons. The drug abuse was always combined with heavy alcohol consumption. One drug abuser had abnormal neurological findings which consisted of lower limb ataxia and 3 others had mild imbalance. MRI examinations did not show differences in width of the third, fourth or lateral ventricles nor the diameter of the cerebral aqueduct but the drug abusers had significantly smaller vermes cerebelli compared to controls. White matter changes also occurred more often in the drug abuser group. These findings are not consistent with known side-effects of the narcotic drugs but more probably a result of very high alcohol consumptions in parallel with drug abuse. Alcohol is clearly a much more potent brain toxic agent than are the most commonly abused narcotic drugs.

Adult↗
PubMed1992

The Chiari type I malformation in two monozygotic twins and first-degree relatives.

The presence of the Chiari type I malformation in 2 adult monozygotic female twins, their mother, and possibly in 2 of their 4 daughters is reported. The diagnosis was made by magnetic resonance imaging and confirmed at the time of surgery in 1 twin. Monozygosity of the twins was proved by DNA typing. The disorder in the present family should probably be classified together with the autosomal dominant craniocervical malformations. Nongenetic factors also seem to be important because the twins were discordant for the extent of herniation of the cerebellar tonsils and the presence of syringomyelia.

Adolescent↗